• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.3
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• pp.60-65
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• 2000

We propose a new method to deal with the optimal gain self-tuning of the PID controller which is used to industrial process control in various fields. First of all, in this method, first order delay system which was modeled from the unit step response of the system is Pade-approximated, then initial values are determined by the Ziegler-Nickels method. Finally, we can find the parameters of Pm controller so as to maximize the fuzzy inferencl function which includes the maximum overshoot, damping ratio, rising time and settling time. The proposed method also shows good adaptability for variations in characteristics and dead time of the system.

• Proceedings of the Korean Reliability Society Conference
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• 2002.06a
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• pp.199-204
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• 2002

본 연구에서는 저압 증기 터빈블레이드의 안전성 확보를 위하여 작용응력 및 강도의 변동성을 고려한 확률론적 해석을 수행하였다. 정상상태에서 작용응력은 이론 및 유한요소해석에 의해서 얻을 수 있으며, 최대 von-Mises 응력은 215.4MPa이다. 회전굽힘 하중하에서의 피로한도는 응력비 R= -1에서 계단식 시험법을 이용하여 구하였으며, 이의 확률론적 특성에 가장 적합한 분포는 3 모수 와이블 분포이다. 그리고 신뢰성에 미치는 다양한 인자들의 영향은 영향계수(sensitivity factor)를 이용하여 정량적으로 평가하였다.

• Journal of Korea Water Resources Association
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• v.46 no.3
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• pp.245-252
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• 2013

The reflection coefficients of monochromatic water waves over various shear currents flowing on a constant topography are estimated analytically in this study. The region of varying shear currents is represented by a finite number of tiny steps with a uniform depth topography. The proper numbers of steps and evanescent modes needed for the analysis are proposed by a series of convergence tests. The characteristics of reflection coefficients for various shear currents conditions are also examined.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.12
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• pp.1475-1483
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• 1992

In this paper, a Fuzzy control approach of disturbance added servo system using MWT(modified windowing technique) was proposed. Because conventional windowing techniques adjust stepwisely a series of scale factors, even small disturbances make system unstable. But the proposed MWT adjusts exponentially. Therefore a servo system which applied this technique had coped excellenlty with internal and external disturbances, and also had decreased substantially steady-state deviation.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1998.06a
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• pp.81-85
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• 1998

점확산 함수(point spread function; PSF)의 정확한 추정은 복원결과가 원 영상에 얼마나 근접할 수 있는가를 결정한다는 점에서 영상처리의 중요한 연구 주제중의 하나가 된다. 본 논문에서는 PSF를 추정하기 위한 알고리즘을 제안하고, 이를 영상복원에 적용한 후 이를 기반으로 디지털 자동초점시스템을 제안한다. 초점불안전 열화시스템을 구현하기 위한 과정은 두 단계로 구성되어 있는데, 즉 입력 영상에서 에지분류를 통한 PSF 추정과, 이를 이용한 영상복원이다. 보다 구체적으로, 입력 영상에 특정 에지가 있는 임의의 크기의 블록을 선정해부면, 그 블록으로부터 자동으로 에지방향이 기저영상을 이용해서 구해지며 확산원의 크기를 추정하여 1차원 단위 계단응답과 영역을 구하여 평균한 후, 2차원 등방성 PSF를 추정한다. 마지막으로 추정된 PSF를 사용하여 복원을 수행함으로써 초점이 맞는 영상을 구한다.

• Korean Journal of Optics and Photonics
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• v.17 no.6
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• pp.493-499
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• 2006

Arbitrary graded-index HOF(Hollow Optical Fibers) are analyzed using the modified Airy function, and the corresponding eigenvalue equation that renders precise results is derived. For graded index HOF, the gradient of an evanescent field in hollow region could be adjusted more sharply than the conventional step-index HOF and the feasibility of more effective atom-guiding is confirmed.

• Journal of the Speleological Society of Korea
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• v.25 no.26
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• pp.131-151
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• 1991

조사대상지역은 제주도 북제주군 한림읍 협재리 협재리국민학교 후편에 위치하고 있는 협재굴과 쌍룡굴, 황금굴, 그리고 양송이 재배장에서 망오름을 향해 2km 떨어진 곳으로 한림으로 나가는길과 교차하는 지점에서 서쪽으로 400-500m 떨어진 곳에 위치하고 있는 소천굴로서 협재굴과 쌍룡굴은 이미 개발되어 관광단지화 되어 있어 입구와 출구는 돌담과 축대를 쌓고 계단을 만들어 완전히 파괴해 버렸으므로 다른 동굴에서 볼 수 있는 동굴입구와 출구의 자연식물경관은 볼 수가 없었고 동백나무를 비롯한 수종의 상록활엽수와 도깨비고비등 수종의 양치식물은 인공적으로 이식해 놓은 실정이다. 황금굴과 소천굴은 아직은 개발이 되지 않고 사람의 접근을 통제하고 있었기 때문에 동굴입구에서 여러 종류의 상록활엽수와 양치식물을 볼 수 있었다. 한편 이들 동굴의 지표면은 인공적으로 조림한 곰솔이 대부분으로 인간간섭을 많이 받은 지역으로 지표면의 식물은 빈약하였다. 또한 이들 동굴의 지층은 표선리 현무암지대로 경사가 완만하며 평탄한 곳으로 이곳의 토양을 분석한 결과 토성은 유기물함량이 7.5%-17.4%로서 척박한 편이며 토양함수량은 9.8%-25.4%로 낮은 편이다.(중략)

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2613-2625
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• 1997

Theoretically, a multi-layered feedforward network has been known to be able to approximate a continuous function to an arbitrary degree of accuracy. However, these networks fail to approximate discontinuous functions when they are trained by well-known training algorithms. This paper presents a training algorithm which doesn't work consists of one or more modules, which are trained in a sequential order within subspaces of the input space, and is trained very rapidely once all modules are trained and merged. The experimantal results of applying this method indicates the proposed training algorithm is superior to traditional ones such as baskpagation.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.694-699
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• 1997

Normal-phase HPLC was used to separate the useful phospholipids, PE, PI and PC in soybean lecithin. The mobile phase used in this experiments were haxane, isopropanol and methanol, the gradient mode was applied as the three components could not be separated by the isocratic mode. To find the optimum separation condition, the concentration profiles of effluents were calculated from the plate theory and the capacity factor in step-gradient mode. From the calculated results, PE was separated with hexane/isopropanol/methanol = 90/5/5vol.% in isocratic mode and PI and PC were resolved in the conditions of 10min gradient time and the second mobile phase of hexane/isopropanol/methanol=50/20/30vol.% in step-gradient mode. The agreement between the calculated concentration profile and experimental data was good, so the methodology developed in this work can be used to obtain the optimum separation condition in gradient mode.

• Nuclear Engineering and Technology
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• v.21 no.1
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• pp.1-11
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• 1989

Numerous losses of decay heat removal capability have occurred at U during stutodwn while its significance to safety is needless to say. A study is carried out as an attempt to assess what could be done to lower the frequency of these events and to mitigate their consequences in the unlikely event that one occurs. The shutdown risk model is developed and analyzed using Event/Fault Tree for the typical pressurized water reactor. The human cognitive reliability (HCR) model, two-stage bayesian approach and staircase function model are used to estimate human reliability, initiating event frequency and offsite power non-recovery probability given loss of offsite power, respectively. The results of this study indicate that the risk of a Pm at shutdown is not much lower than the risk when the plant is operating. By examining the dominant accident sequences obtained, several design deficiencies are identified and it is found that some proposed changes lead to significant reduction in core damage frequency due to loss of cooling events.